1. Field of the Invention
This invention relates to technique about removal of electrostatic charges. Especially, this invention discloses technique about removal of electrostatic charges by using soft X-ray and ceramic having superior thermal characteristics and tungsten in electrostatic charge generating devices in order to remove electrostatic charges effectively.
2. Description of the Related Arts
Generally in LCD, PDP and semiconductor process etc. minute dusts adheres to LCD, PDP and semiconductor wafers according to the generation of electrostatic charges or the dusts cause pattern destruction according to the discharge of electrostatic charges and lowering of yield of products and manufacturing costs increase.
At present in such processes as means for removal of electrostatic charges ion bar and ion blower are used that generate ions by corona discharge but this device generates ions by corona discharge and convects air by fan in order to blow off ionized air. In such processes metallic minute particles under 0.01 μm are generated very much (hundreds of thousands of particles/ft3) at the end part of discharge electrode by the spattering phenomenon according to the high voltage discharge and adhere to it and are separated by forced convection according to a fan and adheres to the surroundings of LCD, PDP and semiconductor patterns to cause inferiority.
O3 gases (ozone) generated by high voltage generation reach 4˜10 ppm and accelerate the adherence of minute dusts as well as the balance of generated +ions and −ions changes frequently to readjust the ion balance every time. Accordingly it became necessary to get a new technique to remove electrostatic charges that does not generate minute dusts and does not need air convection.
FIG. 1 illustrates the principle of removal of electricity of typical voltage-applying type electrostatic remover according to the prior art. As shown in the figure high voltage (10) is applied to ion generation discharging electrode and gases near discharge electrode (20) are ionized by corona discharge between discharging body (40) and electrode and + and −ions are generated. At this time electrostatic charges can be neutralized by the generated + or −ions. Here 30 denotes ion groups generated by the above method. Accordingly it became necessary to get a new technique to remove electrostatic charges that does not generate minute dusts and does not need air convection.
On the other hand nowadays bioscience fields grow rapidly with the development of electronic technologies of high precision system and are based on the air cleaning technology for forming a clean room that is almost clear or germless. However if there exists a discharging body in such a clean room, electrostatic charges become a cause of pollution because minute dusts are absorbed and adhere to it by electrostatic force. Accordingly electrostatic charges that absorb dusts and adhere it become one of main elements affecting to yield of products in clean room like LED, PDP and semiconductor processes. Especially in manufacturing of ultra large scale integrated circuit (ULSI), plasma display panel (PDP) and thin film transistor-liquid crystal display (TFT-LCD), electrostatic charges are electrified easily because SiO2 or glass surface is high insulator. Electrostatic charges generated in the processes lower the reliability of products as well as become a direct cause of lowering the yield of products. Like this, the pollution of adherence of floating minute particles according to the electrostatic charges becomes a very big obstacle to fine processing techniques of semiconductors and only a little pollution may cause a serious affect to the characteristics of semiconductors. Accordingly the necessity of a new charge removing method in order to remove electrostatic charges is rising.
U.S. Pat. No. 5,949,849 is a prior art of this field. This patent relates to an electrostatic charge remover using X-ray generator. A electrostatic charge remover according to this patent has a protective case, an X-ray tube generating soft X-ray, power source device and the X-ray tube has a bulb, a cathode, an output window, an output support, a flange portion, a target and the inner components of the X-ray tube and the protective case are connected thermally and electrically.
Japanese patent 2951477 is another prior art of this field. This patent relates to an electrostatic charge removing technique and removes electrostatic charges of a predetermined charged body under the circumstances including the ions by having a target at inner part of itself, to which a predetermined target voltage and current are given at a position where X-ray is irradiated as for circumstances where a predetermined charged body is arrayed as well as arranging an X-ray tube having a Be window and ionizing elements included in the circumstances of the area, on which X-ray having main wavelength in the range of 2 Å˜20 Å is irradiated from the Be window.
However in the above prior arts the wavelengths of generated X-ray was long and the thermal characteristics of an X-ray generating device was not superior.